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.TH AIO_WRITE 3C "Feb 5, 2008"
.SH NAME
aio_write \- asynchronous write to a file
.SH SYNOPSIS
.LP
.nf
#include <aio.h>

\fBint\fR \fBaio_write\fR(\fBstruct aiocb *\fR\fIaiocbp\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBaio_write()\fR function allows the calling process to write
\fIaiocbp\fR\(->\fBaio_nbytes\fR to the file associated with
\fIaiocbp\fR\(->\fBaio_fildes\fR from the buffer pointed to by
\fIaiocbp\fR\(->\fBaio_buf\fR. The function call returns when the write request
has been initiated or, at a minimum, queued to the file or device. If
\fB_POSIX_PRIORITIZED_IO\fR is defined and prioritized I/O is supported for
this file, then the asynchronous operation is submitted at a priority equal to
the scheduling priority of the process minus \fIaiocbp\fR\(->\fBaio_reqprio\fR.
The \fIaiocbp\fR may be used as an argument to \fBaio_error\fR(3C) and
\fBaio_return\fR(3C) in order to determine the error status and return status,
respectively, of the asynchronous operation while it is proceeding.
.sp
.LP
The \fIaiocbp\fR argument points to an \fBaiocb\fR structure. If the buffer
pointed to by \fIaiocbp\fR\(->\fBaio_buf\fR or the control block pointed to by
\fIaiocbp\fR becomes an illegal address prior to asynchronous I/O completion,
then the behavior is undefined.
.sp
.LP
If \fBO_APPEND\fR is not set for the file descriptor \fIaio_fildes\fR, then the
requested operation takes place at the absolute position in the file as given
by \fIaio_offset\fR, as if \fBlseek\fR(2) were called immediately prior to the
operation with an \fIoffset\fR equal to \fIaio_offset\fR and a \fIwhence\fR
equal to \fBSEEK_SET\fR. If \fBO_APPEND\fR is set for the file descriptor,
write operations append to the file in the same order as the calls were made.
After a successful call to enqueue an asynchronous I/O operation, the value of
the file offset for the file is unspecified.
.sp
.LP
The \fIaiocbp\fR\(->\fBaio_sigevent\fR structure defines what asynchronous
notification is to occur when the asynchronous operation completes, as
specified in \fBsignal.h\fR(3HEAD).
.sp
.LP
The \fIaiocbp\fR\(->\fBaio_lio_opcode\fR field is ignored by \fBaio_write()\fR.
.sp
.LP
Simultaneous asynchronous operations using the same \fIaiocbp\fR produce
undefined results.
.sp
.LP
If \fB_POSIX_SYNCHRONIZED_IO\fR is defined and synchronized I/O is enabled on
the file associated with \fIaiocbp\fR\(->\fBaio_fildes\fR, the behavior of this
function shall be according to the definitions of synchronized I/O data
integrity completion and synchronized I/O file integrity completion.
.sp
.LP
For any system action that changes the process memory space while an
asynchronous I/O is outstanding to the address range being changed, the result
of that action is undefined.
.sp
.LP
For regular files, no data transfer will occur past the offset maximum
established in the open file description associated with
\fIaiocbp\fR\(->\fBaio_fildes\fR.
.SH RETURN VALUES
.sp
.LP
The \fBaio_write()\fR function returns \fB0\fR to the calling process if the
I/O operation is successfully queued; otherwise, the function returns
\fB\(mi1\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
The  \fBaio_write()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
The requested asynchronous I/O operation was not queued due to system resource
limitations.
.RE

.sp
.LP
Each of the following conditions may be detected synchronously at the time of
the call to \fBaio_write()\fR, or asynchronously. If any of the conditions
below are detected synchronously, the \fBaio_write()\fR function returns
\fB\(mi1\fR and sets \fBerrno\fR to the corresponding value. If any of the
conditions below are detected asynchronously, the return status of the
asynchronous operation is set to \fB\(mi1\fR, and the error status of the
asynchronous operation will be set to the corresponding value.
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIaiocbp\fR\(->\fBaio_fildes\fR argument is not a valid file descriptor
open for writing.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The file offset value implied by \fIaiocbp\fR->\fBaio_offset\fR would be
invalid, \fIaiocbp->\fR\fBaio_reqprio\fR is not a valid value, or
\fIaiocbp\fR\(->\fBaio_nbytes\fR is an invalid value.
.RE

.sp
.LP
In the case that the \fBaio_write()\fR successfully queues the I/O operation,
the return status of the asynchronous operation will be one of the values
normally returned by the \fBwrite\fR(2) function call. If the operation is
successfully queued but is subsequently canceled or encounters an error, the
error status for the asynchronous operation contains one of the values normally
set by the \fBwrite()\fR function call, or one of the following:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 13n
The \fIaiocbp\fR\(->\fBaio_fildes\fR argument is not a valid file descriptor
open for writing.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 13n
The file offset value implied by \fIaiocbp\fR->\fBaio_offset\fR would be
invalid.
.RE

.sp
.ne 2
.na
\fB\fBECANCELED\fR\fR
.ad
.RS 13n
The requested I/O was canceled before the I/O completed due to an explicit
\fBaio_cancel\fR(3C) request.
.RE

.sp
.LP
The following condition may be detected synchronously or asynchronously:
.sp
.ne 2
.na
\fB\fBEFBIG\fR\fR
.ad
.RS 9n
The file is a regular file, \fIaiobcp\fR\(->\fBaio_nbytes\fR is greater than 0
and the starting offset in \fIaiobcp\fR\(->\fBaio_offset\fR is at or beyond the
offset maximum in the open file description associated with
\fIaiocbp\fR\(->\fBaio_fildes\fR.
.RE

.SH USAGE
.sp
.LP
The \fBaio_write()\fR function has a transitional interface for 64-bit file
offsets.  See \fBlf64\fR(7).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.sp
.LP
.BR _Exit (2),
.BR close (2),
.BR fork (2),
.BR lseek (2),
.BR write (2),
.BR aio_cancel (3C),
.BR aio_error (3C),
.BR aio_read (3C),
.BR aio_return (3C),
.BR lio_listio (3C),
.BR aio.h (3HEAD),
.BR signal.h (3HEAD),
.BR attributes (7),
.BR lf64 (7),
.BR standards (7)
